CN103414425B - A kind of torque direction of brshless DC motor and the detection method of amplitude - Google Patents

Abstract

The invention relates to a method for detecting the torque direction and amplitude of a brushless direct current motor. The third phase current is calculated through two phase currents in the three phase current; the three rotor position signals are comprehensively calculated to obtain a representative three phase current. The value of the electrical area where the phase current is located; the instantaneous value of the three-phase current and the value representing the three electrical areas are comprehensively calculated to obtain the torque direction; the absolute value of the torque is calculated by the three-phase current; the calculated torque The torque direction is multiplied by the absolute value of the torque, and finally the instantaneous electromagnetic torque of the motor is obtained. The sign of the calculation result represents the torque direction, and the absolute value represents the torque amplitude.

Description

A Detection Method of Torque Direction and Amplitude of Brushless DC Motor

technical field

The invention belongs to the technical field of motor control, relates to the technical field of brushless direct current motor control, and in particular relates to a method for detecting the torque direction and amplitude of a brushless direct current motor.

Background technique

Brushless DC motor has the advantages of simple control, high efficiency, good dynamic response and high reliability, and has been widely researched and applied in the field of servo. Servo motors are often required to have four-quadrant operation control capabilities, that is, forward electric rotation, forward rotation braking, reverse electric rotation and reverse braking, and can be realized through software without changing the motor structure and controller hardware circuit. Forward rotation electric and brake switching, forward braking to reverse electric switching, reverse electric and braking switching, reverse braking to forward electric switching, at the same time, it can start and brake frequently and has a fast dynamic response performance. Usually we realize the four-quadrant operation of the motor for the purpose of controlling the torque. Only by knowing the magnitude and direction of the torque can the four-quadrant operation of the brushless DC motor be accurately controlled.

At present, the methods for detecting the electromagnetic torque direction and amplitude of brushless DC motors generally include the following three methods:

(1) Use the formula Te=Kt×I, where Te is the electromagnetic torque (N m), Kt is the torque coefficient (N m/A), and I is the current (A), where I is generally The bus current of the detected inverter bridge can be obtained by dividing the sum of the absolute values of the three-phase currents by 2, that is, I=i _bus or

In the above torque observation method, the method of using the bus current to observe the electromagnetic torque, because the bus current and the phase current of the three-phase full-bridge inverter of the brushless DC motor control system are not completely equal, so the electromagnetic torque observed by this method The accuracy of the torque is not high; the method of obtaining the observed value of the electromagnetic torque by dividing the sum of the absolute values of the three-phase currents by 2 is relatively accurate, but the formula It can be seen that it can only observe the absolute value of the electromagnetic torque, but cannot reflect the direction of the electromagnetic torque. Therefore, the practicability of this method in practical applications is limited.

(2) Using the formula Calculate the electromagnetic torque, where Te is the electromagnetic torque (N m), e _{x|x=a, b, c} is the opposite potential of the motor (V), ix _{|x=a, b, c} is the current (A), Angular velocity of the ω motor rotor (rad/s).

In the above torque observation method, in addition to the need to obtain the rotational speed and phase current, the most critical thing is to obtain the observed values of the three opposite potentials e _{x|x=a, b, c} . The three opposite potentials can be obtained by measuring the opposite potential waveform and designing It is obtained by means of a potential observer, but in practical applications, it is necessary to detect the continuous signal of the motor rotor position, which is not applicable to the brushless DC motor control system using the Hall position sensor;

(3) Express the electromagnetic torque as the product of the rotor flux linkage and the stator current, using the formula To calculate the torque, where Te is the electromagnetic torque (N m), p is the number of pole pairs of the motor, ψ _rα and ψ _rβ are the a-axis and β-axis flux linkages of the motor rotor in the α-β coordinate system, i _sα and _isβ are the a-axis and β-axis currents of the motor stator in the α-β coordinate system. This method requires the coordinate transformation of the sampled phase current, and at the same time, the observation of the rotor flux linkage is required. The observation of the flux linkage requires the stator current, the resistance and inductance of the stator winding, and the stator voltage. There are many parameters that need to be detected. , in addition, calculation of flux linkage also requires integral calculation, and in integral calculation, changes in stator winding resistance, integral initial value and cumulative error will affect the accuracy of rotor flux linkage calculation;

Among the above three methods, method (1) is not very practical for brushless DC motor torque control; method (2) and method (3) both need to detect continuous rotor position, generally using resolver, photoelectric encoder, etc. A sensor that can continuously detect the rotor position; the algorithm of torque calculation in method (3) is relatively complicated. A great advantage of brushless DC motors in practical applications is the use of simple Hall position sensors. Compared with sensors such as resolvers and photoelectric encoders that detect continuous rotor positions, Hall position sensors occupy less space, are light in weight, and are resistant to It has good vibration performance and is most widely used in brushless DC motor control systems.

Contents of the invention

technical problem to be solved

In order to avoid the deficiencies of the prior art, the present invention proposes a method for detecting the torque direction and amplitude of a brushless DC motor, which is conveniently and simply implemented for brushless DC motors by using Hall position sensors and three-phase phase currents. The detection and calculation method of the direction and amplitude of the electromagnetic torque of the motor.

Technical solutions

A method for detecting torque direction and amplitude of a brushless DC motor, characterized in that the steps are as follows:

Step 1. Calculate the absolute value of the electromagnetic torque of the motor through the three-phase phase current: In the formula: |Te| is the absolute value of the calculated electromagnetic torque; Kt is the torque coefficient of the motor in N m/A; i _a , i _b , and i _c are the phase currents flowing through the three-phase windings of the motor , the unit is A;

Step 2: Through the comprehensive calculation of the three-way brushless DC motor rotor position signals with a phase difference of 120° electrical angle detected by the three Hall position sensors, the values of the electrical regions where the currents currently flowing through the three-phase windings are obtained ,

$\left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; e</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; symbol</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; Hband</span>}\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; Hc</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; Hb</span>}}\mathrm{<span\; class="notranslate">\; andHc</span>}<span\; class="notranslate">\; )</span>\\ {\mathrm{<span\; class="notranslate">\; e</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; symbol</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; Hcand</span>}\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; Ha</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; Hc</span>}}\mathrm{<span\; class="notranslate">\; and\; Ha</span>}<span\; class="notranslate">\; )</span>\\ {\mathrm{<span\; class="notranslate">\; e</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; symbol</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; Haand</span>}\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; Hb</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; Ha</span>}}\mathrm{<span\; class="notranslate">\; andHb</span>}<span\; class="notranslate">\; )</span>\end{array}\right.$

Among them: e _x _symbol (x=a, b, c) is the value of the electric current area, represented by three values -1, 0, +1, "-1" means in this area, and x (x=a ,b,c) The phase current of x(x=a,b,c) corresponding to the opposite potential is not zero and the waveform function of the opposite potential is negative; "+1" means that in this area, it is the same as x(x=a ,b,c) The phase current of x (x=a,b,c) corresponding to the opposite potential is not zero and the waveform function of the opposite potential is positive; b, c) The x, (x=a, b, c) phase current corresponding to the opposite potential is zero, and the value of the waveform function of the opposite potential is a value greater than -1 and less than +1 related to the rotor position; hall signal Represents the "logical NOT" calculation of its signal, and "and" is the "logical AND"calculation;

Step 3. Comprehensively calculate the current flowing through the three-phase windings and the values representing the three electrical areas:

Te _sign ＝sign(i _a ×e _a _symbol+i _b ×e _b _symbol+i _c ×e _c _symbol)

Among them, Te _sign ——electromagnetic torque sign variable, the calculation result is represented by -1, +1, 0, -1 means that the torque is negative, +1 means that the torque is positive, and 0 means that the torque is zero; sign(x )—symbolic calculation function, $\mathrm{sign}\left(x\right)=\left\{\begin{array}{c}+1,x>0\\ 0,x=0\\ -1,x<0\end{array}\right.;$

Step 4: Multiply the calculated absolute value of the motor torque |Te| with the calculated torque sign Te _sign to obtain the brushless DC motor torque value

$\mathrm{<span\; class="notranslate">\; Te</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; sign</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; e</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; symbol</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; e</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; symbol</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; e</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; symbol</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&times;</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; Kt</span>}<span\; class="notranslate">\; (</span><span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; |</span><span\; class="notranslate">\; +</span><span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; |</span><span\; class="notranslate">\; +</span><span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; |</span><span\; class="notranslate">\; )</span>$

The sign of the above calculation result is the torque direction, and the absolute value is the torque amplitude.

The unknown current of any phase in the three-phase phase currents is obtained by the measured phase currents of any two phases in the three-phase phase currents: i _c =-i _a -i _b , where i _a represents the first phase current sampling value, _ib represents the current sampling value of the second phase B, and _ic represents the current value of the unknown phase.

Beneficial effect

The method for detecting the torque direction and amplitude of a brushless DC motor proposed by the present invention only needs to detect the rotor position of the brushless DC motor and the current flowing through the phase windings, without detecting phase voltages, opposite potentials, and knowing For parameters such as motor stator resistance and inductance, the detection device does not participate in the calculation; the rotor position detection of the brushless DC motor only needs to detect three discrete rotor position signals with a mutual difference of 120° electrical angle through the rotor position sensor, without detecting the continuous rotation of the rotor position. Change value; the calculation method can be realized by programming the programmable chip, which only occupies software program space and does not occupy physical hardware space. Therefore, the present invention requires few electrical parameters to be detected, and the required hardware structure and calculation method are simple.

Description of drawings

Fig. 1 is the schematic block diagram of the brushless DC motor speed-torque double closed-loop control system of the preferred embodiment of the present invention, it comprises the torque direction and amplitude detection device and calculation method realized according to the present invention;

Fig. 2 is the hardware block diagram of the brushless DC motor speed-torque double closed-loop control system of the preferred embodiment of the present invention, and it comprises the detecting device of torque direction and amplitude realized according to the present invention;

Fig. 3 is the algorithm calculation block diagram of the torque direction and amplitude detection calculation method of the preferred embodiment of the present invention;

Fig. 4 is according to the preferred embodiment of the present invention torque direction and magnitude device and calculation method the motor rotor position signal and the electric area relation solution algorithm schematic diagram of the current that flows through the three-phase winding at present;

Fig. 5 and Fig. 6 are diagrams of time sequence relationship diagrams of motor electromagnetic torque, Hall position sensor signal, current phase current, opposite potential, and phase current electrical regions in a preferred embodiment of the present invention;

FIG. 7 is a schematic block diagram of a (but not the only) variation of the schematic diagram of solving the relationship between the motor rotor position signal and the electrical region where the current flowing through the three-phase windings is shown in FIG. 4 .

Detailed ways

Now in conjunction with embodiment, accompanying drawing, the present invention will be further described:

Torque direction and amplitude detection device: three Hall position sensors (2) and signal detection circuit (3). The Hall position sensor is a device used to detect the rotor position of the brushless DC motor. It is generally installed inside the brushless DC motor. The motor rotor position signal detected by the Hall position sensor has the same phase difference of 120° according to the rotation direction of the motor. The phase relationship of the angle; the Hall position sensor signal detection circuit is used to convert the signals output by the three Hall position sensors into a logic level that can be processed by the subsequent circuit through direct transmission, optocoupler device isolation or magnetic coupler device isolation, etc. Signal.

A current sensor (4) and its signal conditioning circuit (5) for detecting the current flowing through the phase winding. The function of the signal conditioning circuit is to convert the signal output by the current sensor into a voltage signal that can be accepted by the programmable chip or ADC (Analog to Digital Converter) in the system, and is used to convert the analog signal of the current into a voltage signal for calculation digital signal;

An ADC chip and peripheral circuits (6) for realizing analog-to-digital conversion. It is used to convert the analog voltage representing the current into a digital value representing the magnitude of the phase current and its positive and negative values, and output it to the subsequent programmable chip for torque calculation; the ADC can be an external programmable chip integrated with the ADC function module It can also be independent of a separate ADC chip and peripheral circuits of the programmable chip;

The programmable chip (7) used to realize the calculation of torque direction and amplitude, the programmable chip should be a programmable chip with ADC peripherals, or an independent programmable chip, and the ADC is a separate chip, and the programmable chip can Read the digital quantity representing the current output by the ADC into the chip;

The brushless DC motor adopts the operation mode of two-phase conduction, three-phase star and six states. The waveforms of the opposite potentials e _a , e _b , and e _c of the brushless DC motor are trapezoidal waves with a mutual difference of 120° electrical angle. , the flat top width of the trapezoidal wave is 120° electrical angle, and the period of the trapezoidal wave is 360° electrical angle.

At any time, the electromagnetic power of the brushless DC motor is the sum of the electromagnetic power of the three-phase windings, so there is

P=e _a i _a +e _b i _b +e _c i _c (6)

And because the relationship between the electromagnetic power of the motor, the electromagnetic torque and the angular velocity of the rotor is

${\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; e</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; P</span>}}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 7</span>}<span\; class="notranslate">\; )</span>$

Among them, T _e ——the electromagnetic torque of the motor, the unit is N·m,

ω——The angular velocity of the motor, in rad/s,

P——The electromagnetic power of the motor, the unit is W

From the above two formulas, it can be known that the electromagnetic torque of the brushless DC motor is

${\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; e</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; e</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; e</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; e</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 8</span>}<span\; class="notranslate">\; )</span>$

In the case of not considering freewheeling, the currents of each phase are not zero at the flat top part of their corresponding opposite potential waveforms, and the rest are zero. Therefore, in the above formula, it is only necessary to consider the positive and negative flat tops of each opposite potential , and e _x ＝Ke·ω·f _x (θ),(x=a,b,c), where f _x (θ),(x=a,b,c) is the opposite potential waveform function ( On the contrary, the potential waveform function is a dimensionless function with a period of 360° electrical angle, a flat top width of 120° electrical angle, and a peak value of +1 or -1 at the flat top of the waveform), so the calculation formula of the above electromagnetic torque can be transformed into

T _e ＝Ke×(f _a (θ)i _a +f _b (θ)i _b +f _c (θ)i _c ) (9)

Analyzing the corresponding relationship between the three-way Hall signals and the three opposite potential waveform functions of the motor in Figure 5 and Figure 6, it can be concluded that the calculation relationship between the value at the flat top of the trapezoidal wave opposite potential waveform function and the three-way Hall signals is as follows:

$\left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; e</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; symbol</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; Hband</span>}\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; Hc</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; Hb</span>}}\mathrm{<span\; class="notranslate">\; andHc</span>}<span\; class="notranslate">\; )</span>\\ {\mathrm{<span\; class="notranslate">\; e</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; symbol</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; Hcand</span>}\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; Ha</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; Hc</span>}}\mathrm{<span\; class="notranslate">\; and\; Ha</span>}<span\; class="notranslate">\; )</span>\\ {\mathrm{<span\; class="notranslate">\; e</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; symbol</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; Haand</span>}\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; Hb</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; Ha</span>}}\mathrm{<span\; class="notranslate">\; andHb</span>}<span\; class="notranslate">\; )</span>\end{array}\right.<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 10</span>}<span\; class="notranslate">\; )</span>$

Among them, e _x _symbol, (x=a, b, c)——the calculated value of the current electrical area, represented by three values of -1, 0, and +1, "-1" means that within this area, it is the same as x(x =a,b,c) The phase current of x(x=a,b,c) corresponding to the opposite potential is not zero and the waveform function of the opposite potential is negative; "+1" means that in this area, it is the same as x(x =a,b,c) The phase current of x (x=a,b,c) corresponding to the opposite potential is not zero and the waveform function of the opposite potential is positive; "0" means that in this area, it is consistent with x (x= a, b, c) The phase current corresponding to x, (x=a, b, c) of the opposite potential is zero, and the value of the waveform function of the opposite potential is a value greater than -1 and less than +1 related to the rotor position, but , it can be seen from the electromagnetic torque formula of the motor that when the phase current corresponding to the opposite potential is zero, the motor does not generate electromagnetic torque, and when the phase current of x(x=a,b,c) is zero, x(x = a, b, c) The opposite potential is meaningless for the electromagnetic torque, so, in the calculation formula of the variable ex _symbol, ( _x =a, b, c), the ex _symbol of this area, ( _x =a ,b,c) values are resolved as an algebraic value that is numerically zero and has nothing to do with the opposite potential waveform function.

Among them, "and" means logical "and" operation, and "-" means subtraction calculation. The above calculation formula is a mixed operation of logical operation and algebraic operation. The ones inside the brackets are logical operations, and the ones outside the brackets are algebraic operations. Here The meaning of the brackets is to convert the two Boolean values of "0" and "1" generated by the result into two real numbers of "0" and "+1" after performing the logical operation inside the brackets, and then perform signed algebraic operations.

Therefore, without considering commutation and freewheeling, the electromagnetic torque formula of the motor can be expressed as

$\mathrm{<span\; class="notranslate">\; Te</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; Kt</span>}<span\; class="notranslate">\; \&times;</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; e</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; symbol</span>}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; e</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; symbol</span>}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; e</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; symbol</span>}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 11</span>}<span\; class="notranslate">\; )</span>$

Among them, Kt=2Ke, Kt—torque coefficient, the unit is N m/A; Ke—the opposite potential coefficient, the unit is V/(rad/s).

The brushless DC motor usually adopts the operation mode of two-phase conduction and three-phase star six states. In the non-commutation stage, only two phases are conduction at any time, and the phase current of the other phase is zero. The relationship between the three-phase currents is

$\left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\\ {\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}\end{array}\right.<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 12</span>}<span\; class="notranslate">\; )</span>$

Among them, i ₁ —— conduction phase current 1;

i ₂ ——conduction phase current 2;

i ₃ ——Non-conducting phase current.

When considering the freewheeling current during commutation, the three-phase current still has the following relationship during the commutation phase

i _a + i _b + i _c = 0 (13)

Therefore, from formula (9), Kt=2Ke and the corresponding relationship between phase current, back EMF waveform function and electromagnetic torque in Figure 5 and Figure 6, it can be known that the absolute value of the electromagnetic torque of the brushless DC motor can be expressed as

$<span\; class="notranslate">\; |</span>\mathrm{<span\; class="notranslate">\; Te</span>}<span\; class="notranslate">\; |</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; Kt</span>}<span\; class="notranslate">\; \&times;</span><span\; class="notranslate">\; (</span><span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; |</span><span\; class="notranslate">\; +</span><span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; |</span><span\; class="notranslate">\; +</span><span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; |</span><span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 14</span>}<span\; class="notranslate">\; )</span>$

Although formula (11) has a certain error in the calculation result of the electromagnetic torque when commutation freewheeling is considered, its calculation result for the electromagnetic torque sign is accurate, so it can be used as the calculation of the electromagnetic torque sign The formula, so the calculation formula of the electromagnetic torque sign can be expressed as

Te _sign ＝sign(i _a ×e _a _symbol+i _b ×e _b _symbol+i _c ×e _c _symbol) (15)

Among them, Te _sign ——electromagnetic torque sign variable, the calculation result is represented by -1, +1, 0, -1 represents that the torque is negative, +1 represents that the torque is positive, and 0 represents that the torque is zero;

sign(x) - sign calculation function

$\mathrm{<span\; class="notranslate">\; sign</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\left\{\begin{array}{c}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; ></span>\mathrm{<span\; class="notranslate">\; 0</span>}\\ \mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}\\ <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; 0</span>}\end{array}\right.<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 16</span>}<span\; class="notranslate">\; )</span>$

So far, the brushless DC motor torque direction and amplitude detection and calculation method of the present invention can be expressed by the following equations:

$\left\{\begin{array}{c}\mathrm{<span\; class="notranslate">\; Te</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; sign</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; e</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; symbol</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; e</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; symbol</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; e</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; symbol</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&times;</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; Kt</span>}<span\; class="notranslate">\; \&times;</span><span\; class="notranslate">\; (</span><span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; |</span><span\; class="notranslate">\; +</span><span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; |</span><span\; class="notranslate">\; +</span><span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; |</span><span\; class="notranslate">\; )</span>\\ {\mathrm{<span\; class="notranslate">\; e</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; symbol</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; Hband</span>}\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; Hc</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; Hb</span>}}\mathrm{<span\; class="notranslate">\; andHc</span>}<span\; class="notranslate">\; )</span>\\ {\mathrm{<span\; class="notranslate">\; e</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; symbol</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; Hcand</span>}\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; Ha</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; Hc</span>}}\mathrm{<span\; class="notranslate">\; and\; Ha</span>}<span\; class="notranslate">\; )</span>\\ {\mathrm{<span\; class="notranslate">\; e</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; symbol</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; Haand</span>}\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; Hb</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; Ha</span>}}\mathrm{<span\; class="notranslate">\; andHb</span>}<span\; class="notranslate">\; )</span>\end{array}\right.<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 17</span>}<span\; class="notranslate">\; )</span>$

The sign of the calculation result of Te in the above formula represents the direction of the torque, and the numerical value represents the magnitude of the torque.

As can be seen from the above analysis, if the torque direction and amplitude detection device and calculation method of the brushless DC motor of the present invention are to be used to calculate the electromagnetic torque of the motor, the following specific steps need to be implemented:

(1) Build and debug three Hall position sensors and their signal conditioning circuits, and send the final output three-way discrete rotor position signals to the programmable chip;

(2) Build and debug the current sensor circuit for any two-phase current of the motor, the conditioning circuit for the output signal of the current sensor, ADC and its peripheral circuits, sample and convert any two-phase current of the motor into signed digital quantities, and send into the programmable chip;

(3) Implement the electromagnetic torque calculation algorithm shown in formula (17) in the programmable chip, and the torque coefficient in formula (17) can be calculated by formula (18)

$\mathrm{<span\; class="notranslate">\; Kt</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; Te</span>}}_{\mathrm{<span\; class="notranslate">\; N</span>}}}{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; N</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 18</span>}<span\; class="notranslate">\; )</span>$

Among them, Te _N - the rated torque of the motor, the unit is N m;

I _N ——The rated current of the motor, the unit is A.

(4) Figure 5 and Figure 6 illustrate the timing relationship of electromagnetic torque, Hall position sensor signal, current phase current, opposite potential, and phase current electrical area. In Fig. 5 and Fig. 6, i _a , i _b , i _c (A) are the phase current signals, the unit is ampere (A), and _{ex_symbol} (x=a, b, c) is the calculated value of the three-phase current electrical area , f _x (θ) (x=a, b, c) has nothing to do with the rotational speed and has no unit back EMF waveform function, Ha, Hb, Hc represent the three Hall signals of the rotor position of the motor, Te is calculated by the present invention The electromagnetic torque calculated by the method, the unit is Newton·meter (N·m).

The waveform curves of each variable in Fig. 5 and Fig. 6 respectively represent the a phase, b phase or c phase signal corresponding to the system of the preferred embodiment of the present invention as shown in the figure, which specific curve corresponds to the signal of which phase , in a specific application, it can also be freely exchanged according to the habit of the programmer or the specific situation, provided that the calculation logic between the signals still needs to follow the calculation logic shown in Figure 4.

(5) Table 1 shows the calculation results of the three-phase current electrical area calculation method shown in Figure 5 and Figure 6 according to the timing relationship in Figure 4 and Equation (10). In Table 1, when the Hall signals are all 0 or all 1, it indicates that the Hall signal circuit is faulty. At this time, according to formula (10), the values representing the phase current electrical region will all be resolved to 0.

Table 1

Claims (1)

1. the torque direction of brshless DC motor and a detection method for amplitude, is characterized in that step is as follows:

Step 1, calculate motor electromagnetic torque absolute value by three-phase phase current: in formula: | Te| is the absolute value of the electromagnetic torque calculated; Kt is the moment coefficient of motor, and unit is Nm/A; i _a, i _b, i _cfor flowing through the phase current of motor 3 phase winding, unit is A;

Step 2: three road brushless DC motor rotor position signallings of the phase place mutual deviation 120 ° of electrical degrees detected by three hall position sensors carry out COMPREHENSIVE CALCULATING, obtains the current numerical value flowing through the electrical areas at the electric current difference place of three-phase windings,

$\left\{\begin{array}{c}{e}_a\_symbol=\left(Hband\stackrel{\&OverBar;}{Hc}\right)-\left(\stackrel{\&OverBar;}{Hb}andHc\right)\\ e_b\_symbol=\left(Hcand\stackrel{\&OverBar;}{Ha}\right)-\left(\stackrel{\&OverBar;}{Hc}andHa\right)\\ e_c\_symbol=\left(Haand\stackrel{\&OverBar;}{Hb}\right)-\left(\stackrel{\&OverBar;}{Ha}andHb\right)\end{array}\right.$

Wherein: e _x_ symbol (x=a, b, c) be the numerical value in current electrical region, with-1,0 ,+1 three numeric representation, "-1 " represents in this region, with x (x=a, b, c) x (x=a, b, the c) phase current that opposite potential is corresponding is non-vanishing and this opposite potential wave function is negative value; "+1 " represents in this region, non-vanishing and this opposite potential wave function of x (x=a, b, the c) phase current corresponding with x (x=a, b, c) opposite potential be on the occasion of; " 0 " represents in this region, the x corresponding with x (x=a, b, c) opposite potential, and (x=a, b, c) phase current is zero, and the value of this opposite potential wave function is be greater than-1 numerical value that is less than+1 relevant with rotor-position; hall signal " logic NOT " that represent its signal calculates, and " and " is that " logical AND " calculates;

Step 3, the electric current flowing through three-phase windings and the numerical value representing three electrical areas are carried out COMPREHENSIVE CALCULATING:

Te _sign＝sign(i _a×e _a_symbol+i _b×e _b_symbol+i _c×e _c_symbol)

Wherein, Te _sign---electromagnetic torque symbolic variable, result of calculation represents with-1 ,+1,0, and-1 to represent torque be negative, and+1 represents torque for just, and 0 to represent torque be zero; Sign (x)---sign computation function, $sign\left(x\right)=\{\begin{array}{cc}+1,& x>0\\ 0,& x=0\\ -1,& x<0\end{array};$

Step 4: by the motor torque absolute value calculated | Te| and the torque sign Te calculated _signbe multiplied, draw brshless DC motor torque numerical value

$Te=sign(i_a\&times;e_a\_symbol+i_b\&times;e_b\_symbol+i_c\&times;e_c\_symbol)\&times;\frac{1}{2}Kt\&times;\left(\right|i_a|+|i_b|+|i_c\left|\right)$

The symbol of above-mentioned result of calculation is torque direction, and absolute value is torque amplitude;

The phase current that in described three-phase phase current, arbitrary phase unknown current has been surveyed by any two-phase in three-phase phase current draws: i _c=-i _a-i _b, in formula, i _arepresent first-phase current sampling data, i _brepresent second-phase current sampling data, i _crepresent the current value of unknown phase.